The present invention relates to the servicing of heat exchangers and, more particularly, to a device for engraving or stamping identification characters at each tube location in the tube sheet of a steam generator.
In many respects, nuclear steam generators are similar to other large heat exchangers, in that a multiplicity of tubes are connected to a tube sheet in a head region of a large pressure vessel. Periodically, different maintenance procedures must be performed on at least some of the tubes. The unique characteristic of nuclear steam generators is that tube maintenance or repair procedures must be performed in a highly radioactive environment, which necessitates the use of remotely controlled servicing equipment.
The nuclear industry has developed an extensive array of specialized equipment for cleaning, inspecting, plugging, sleeving, repairing and otherwise servicing individual steam generator tubes during outages. However, since most nuclear steam generators include anywhere between 5,000 to 10,000 tubes, the identification of particular tubes for performing the servicing procedures has posed considerable difficulties to maintenance personnel. A related problem has been the difficulty of verifying that the intended tube was in fact tested or serviced in a way that satisfies the records requirements associated with quality assurance regulations.
Conventionally, the identification and verification of individual tubes has been accomplished by a combination of human and electronic vision, i.e., direct observation for short time intervals to avoid human exposure to excessive radiation, coupled with television or other optical devices.
This has proven unreliable and thus the need exists for an improved technique for the identification of the tubes at the tube sheet.